1. Field of the Invention
This invention relates to cooling of components having non-film cooled hot surfaces for disposal and use in a hot flowpath, and more particularly to, combustor liners having non-film cooled hot surfaces.
2. Description of Related Art
It is well known to cool parts using heat transfer across walls having hot and cold surfaces by flowing a cooling fluid in contact with the cold surface to remove the heat transferred across from the hot surface. Among the various cooling techniques presently used are convection, impingement, and film cooling. These cooling techniques have been used to cool gas turbine engine hot section components such as turbine vanes and blades and combustor liners. Film cooling has been shown to be very effective but requires a great deal of fluid flow which typically requires the use of power and is therefore generally looked upon as fuel efficiency and power penalty in the gas turbine industry.
Cooling methods that pass cooling air through the combustor liner have been found to be detrimental to the control of NOx emissions. Designers of low NOx emission combustors seek to eliminate or minimize the amount of cooling air introduced into the combustion zone, thus discarding the high efficiency film cooling methods. Therefore, it is highly desirable to cool the combustor liner using convective and/or impingement cooling which are not as effective in reducing liner temperature.
Another drawback to film cooling is the degree of complexity in fabricating and machining the components. In the past slot film cooling and more recently angled multi-hole film cooling techniques have been developed for particular use in combustor liners. Turbine airfoils on both blades and vanes often incorporate film cooling holes to flow cooling air along the hot surfaces of the airfoil walls. Film cooling slots and angled holes require a great deal of fabrication and or machining. The wall structures themselves are weakened by the cooling airflow passages required to flow the cooling air from the cold to the hot surfaces.
The present invention was developed to improve non-film cooling techniques for gas turbine engine combustor liners so as to efficiently cool the liners without resorting to film cooling and the drawbacks discussed above that are associated with such techniques.